The Evaluation of Novel Bioactive Ingredients for Combat Ration Intermediate Moisture (IM) Products to Assure the Microbiological Safety

Military intermediate moisture (IM) sandwiches have a shelf life requirement of two years at 80 degrees F. The stability of IM sandwiches is maintained using Hurdle technology, which typically provides a pH below 5.5 and a water activity below 0.89. These levels are effective for microbial stability; however, they can have an effect on the sensory quality of the product and can limit the development of new products. This report describes a series of challenge studies to raise both levels. Two IM products, the Italian pocket sandwich (IPS) and the bacon cheddar sandwich (BCS) were reformulated to a pH above 6 and a water activity above 0.9. Various bioactive ingredients (BIs) were then added to the reformulations (as an additional hurdle), in the form of Purasal(R)P (lactate/diacetate), epsilon-polylysine, or Nisaplin (R)(nisin), to provide microbial stability. The studies were conducted on the reformulated products with five different strains of Staphylococcus. aureus, which would be the most likely microbial contaminant in these products. The studies were carried out for 180 days at 25 degrees C. For the IPS the three BIs were incorporated into both the bread and the filling. It was determined that 4% purasal, 2.5% epsilon-polylysine, and 1.2% nisin were effective in inhibiting the growth of S. aureus. For the BCS only purasal and nisin were incorporated. They were added in the same concentrations as in the IPS, but were incorporated only in the bread. Results were similar; however, there was less S. aureus growth in the BCS control than in the IPS control. Though all three ingredients inhibited the growth of S. aureus, nisin appeared to be the most effective based on its ability not only to inhibit growth, but also to reduce the original bacterial population. It also had less effect on the sensory properties.